In general, the traction drive mechanism is preferably of as small a size as possible from a viewpoint of energy-saving. Furthermore the traction drive unit is used under high-speed and high-load conditions. Hence a traction drive fluid for use in the traction drive mechanism is desired to be of low viscosity and to be capable of maintaining a high traction coefficient even at elevated temperatures, that is, to be able to use satisfactorily under such severe conditions.
Various compounds have heretofore been proposed as traction drive fluids, including the compounds as described in Japanese Patent Publication Nos. 338/1971, 339/1971, 35763/1972, 42067/1973, 42068/1973, and 36105/1978, and Japanese Patent Application Laid-Open Nos. 43108/1980 and 40726/1980. These compounds, however, have disadvantages in that the traction coefficient drops as the temperature rises, or although the traction coefficient does not drop, the viscosity is high and the stirring loss in the traction drive mechanism is large.